Improvement in drill-bits



No. 38,119. Patemed Apg. 7. 1863. Y

UNITED STATES PATENT OFFICE.

IMPROVEMENT IN DRILL-BITS.

Specication forming part of Letters Patent No. 38,119, dated April 7,1863.

To all whom. it may concern.-

Be it known that I, STEPHEN AMBRosE MORSE, of East Bridgewater, in thecounty of Plymouth and State of Massachusetts, have invented `a new anduseful Improvement in Drills 5 and I do hereby declare that thefollowing is a full and exact description of the construction and use ofthe same, reference being had to the accompanying drawings, and to theletters and figures marked thereon.

Figure I is a front view of the drill. Fig. II is a View of the end ofthe drill. Fig. III is a section on the line A B, Fig. I. Fig. IV is asection of one of the grooves on the line C D, Fig. l. Fig. V shows theshape of the bottom of the drill.

The object of my improvement in twist drills is to secure a sharp andstraight cutting-edge, presented to the me'tal at a suitable angle andhaving such a form of the groove, when seen in cross section, as willproduce the straight cutting-edge when the drill is ground at theordinary angle.

The common drill scrapes the metal that is to be drilled, while my drillcuts the metal and discharges the chips and borings without clogging.

l'he drill is made, by the use of revolving cutters or burrs, from asolid cylindrical rod, E F G, Fig. I, and when in use is held by theupper part, E F. Thclower part, F G, hasa double spiral groove, P H, cutupon it, the

Vgeneral appearance of which resembles those in common use, but thedifference consists in this, that the section of the groove at any pointthroughout its length, as at G D, is nearly of the form shown in Fig.IV, the right side ofthe groove being a short, quick curve, and nearlyin the direction of the radius, while the left or Vopposite side of thegroove is a longer or more shallow curve. The form of the end of thedrill when ground is shown in Fig. II, the direction of the cuttingedges or lips being shown by the parallel lines I Q. In Fig. V thecutting-edges of the double groove are represented at J and J Theperiphery on opposite sides of the drill is seen at K K', while thecurves L L are of such a shape as to allow as large a mass of metal aspossible in the direction of the dotted lines S J and S J for thepurpose of giving a strong support to the cutting-edges which revolve inthe direction of the arrow.

When the drill is ground, which should be at about the angle representedin Fig. I, the cutting-edges J J form nearly a straightline, and justback of the edge the curvature of the grooves F and H is such as to forman acute angle, instead of a right angle, as in the common twist-drill.The peculiar shape of the groove is retained throughout its wholelength, and as the drill is gradually shortened by grinding the shape ofthe cutting-edge remains unchanged.

From the above description it will be perceived that I have produced atwistdrill, having an acutefangled edge extending in the direction ofthe radius and strengthened by the mass of metal in the rear of the edgeor lip.

I make the spiral grooves with an increasing twistthat is to say, thedistance from one spiral to another in the direction of the axis isgreater at the upper part of the drill than it is near the point, asshown in Fig. I, the space between the lines O and N being greater thanit is between N and M. This increasing twist enla-rges the space inwhich the borings are received, and they traverse the groove more nearlyin aline with the axis, and consequently with less friction.

A drill made in the manner herein described will make a perfectlystraighthole. It willnot diverge from its course while passing throughblow holes or soft and hard places. The edge actually cuts the metal,thus diminishing the friction and wear of the edge. The borings or chipsare discharged freely, and the edge is strongest at the periphery, wherethe strain is greatest.

What I claim, and' desire to secure by Letters Patent, is

1. A twistdrill, in which the spiral grooves are so cut or formed thatthe curvature of that side of the groove which makes the cuttinged ge isvery nearly in the direction ot the radius, and when the drill is groundat the ordinary angle presents a straight and acuteangled edge or lip tothe metal or other substance that is to be drilled.

2. In combination with the form of the groove, as above set forth, theincrcasin g twist to facilitate the discharge of the borings or chips.

STEPHEN A. MORSE. In presence of- J AMES EATON, SILAs BURGEss.

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